1. Field of the Disclosure
The disclosure generally relates to safety devices for gas distribution systems, and specifically relates to slam-shut type safety valves.
2. Related Technology
Gas distribution systems, in particular natural gas distribution systems, typically transport gas from a producer to a consumer along a series of pipes and through a series of valves. Each gas distribution system may include one or more regulator valves that control the pressure of the gas within the distribution system. Normally, the gas is transmitted at a high pressure through the system. However, the pressure of the gas must be reduced prior to final distribution to the consumers. This pressure reduction is typically accomplished at pressure reducing stations within local networks.
Typically, these pressure reducing stations include one or more pressure regulating valves and some sort of safety device to shut off the flow of gas should the pressure regulating valve fail. Most commonly, slam-shut safety valves are used for this purpose. For example, U.S. Pat. No. 4,134,421, which is hereby incorporated by reference, discloses a slam-shut safety valve that provides overpressure protection in a pipeline. The slam-shut safety valve is generally disposed upstream of the pressure regulating valve so that the slam-shut valve may prevent gas from reaching the pressure regulating valve in the event of a pressure regulating valve failure. The slam-shut safety valve monitors gas pressure downstream of the pressure regulating valve for maximum and minimum pressure tolerances. If the downstream pressure exceeds either the maximum or minimum tolerance, the slam-shut safety valve closes, cutting off the flow of gas to the pressure regulating valve and preventing an uncontrolled leak of gas due to the pressure regulating valve failure.